As I mentioned in a video a bit back I wanted to add more water to the geothermal water system. This will improve the systems ability to absorb and store more energy. This should improve cooling in the summer and heating in the winter. I decided to place a 55 gallon drum to the rear of the greenhouse. Additionally, to maximize the system performance, I wanted to add radiant heating/cooling pipes in the aisle between the beds. This will increase the surface area greatly.
It took several weeks to get all the parts and plan the attack. But once the parts and plans were in place, it only took a couple hours to retrofit the greenhouse with the upgrade. Here’s step-by-step what I did with images.
Here’s an image from about a week earlier showing what we are working with. The bed on the left is regulated with the geothermal water system. It has PEX tubing running through the bottom of the bed. We are going to attach to that tubing and run 4 more lengths up and down the center aisle between the two beds. At the end of the aisle we will put the 55gal drum.
Step 1 – remove tiles and dig trenches
This was pretty straight forward. I made the trenches about 2-3″ deep. The first trench and last trench hugged the edge of the bed. In the middle, I made the trench deep and wide enough for two passes. The reason for this is I needed exactly 4 passes but the aisle just wasn’t quite wide enough for that with 9 inch spacing between the passes. The aisle is just under 3 feet. If it was exactly 3 feet, it would have been perfectly spaced.
Step 2 – Lay out PEX
PEX really doesn’t want to be straight. Putting some dirt over the ends helped me hold it down enough to get it in the trenches.
Step 3 – Cover PEX
While digging the trenches, I move the dirt to a wheelbarrow. I moved it back after laying out the PEX. I also added a layer of sand to help level the aisle. I used 4 50lb bags of sand from Home Depot.
Step 4 – Clean tiles
The tiles got kinda dirty over the last 9 months. This is a good opportunity to clean them off. These tiles are made from recycled rubber tires. The cleaned easily with a hose.
Step 5 – Weed cover and replace tiles
I put down two layers of weed cover. Mostly because it was already rolled as two layers and the length was perfect for the aisle. Rather than unfolding the layers, I just laid it out as it was rolled.
Step 6 – Connect barrel to system
The PEX is 1/2 inch. I bought some braided PVC tubing of the same inner-diameter to match. I connected them together with several barb couplers. For the barrel, I drilled holes in the bung-cap and put some 1/2 inch NPT threaded bulkheads. The bungs for this barrel are not the same as I’m used to. These drums are of Japanese origin and it took some extra planning to make adapters for them.
To get the pex to fit on the plastic barbs, I had to heat it up to soften it. The fit still wasn’t great. Brass barbs fit better.
Step 7 – Fill the barrel
This was slightly tricky. My reservoir is 20 gallons. It fills from 1/4 inch tubing from my rain water barrels via a float valve. The geothermal water system is all 1/2 inch. Output is greater than input. So to fill the 55 gallon barrel, I needed to add more water as needed to the reservoir. I used my garden hose to add water when needed. I had to fill it a couple times after it got low.
Note: this may look not level… and it is, but not as much as you might think. First, the left post of the greenhouse settled about 6 inches. Second, the barrel is under pressure and is bulging a bit making it lean more to the right. The bulging is concerning. I fix might include a reducer before the inlet.
After filling it with water and tightening up a few hose clamps, it was finished. Let’s enjoy some fresh garden strawberries and celebrate the new 20 megawatts I’ve just added to the system. This brings my total up to 27mW (20 gallon tank is 7mW at 23C).